Epigenetic Regulation of KPC1 Ubiquitin Ligase Affects the NF-κB Pathway in Melanoma.

Abnormal activation of the NF-κB pathway induces a more aggressive phenotype of cutaneous melanoma. Understanding the mechanisms involved in melanoma NF-κB activation may identify novel targets for this pathway. KPC1, an E3 ubiquitin ligase, is a regulator of the NF-κB pathway. The objective of this study was to investigate the mechanisms regulating KPC1 expression and its clinical impact in melanoma. The clinical impact of KPC1 expression and its epigenetic regulation were assessed in large cohorts of clinically well-annotated melanoma tissues (tissue microarrays; = 137, JWCI cohort; = 40) and The Cancer Genome Atlas database (TCGA cohort, = 370). Using melanoma cell lines, we investigated the functional interactions between KPC1 and NF-κB, and the epigenetic regulations of KPC1, including DNA methylation and miRNA expression. We verified that KPC1 suppresses melanoma proliferation by processing NF-κB1 p105 into p50, thereby modulating NF-κB target gene expression. Concordantly, KPC1 expression was downregulated in American Joint Committee on Cancer stage IV melanoma compared with early stages (stage I/II = 0.013, stage III = 0.004), and low KPC1 expression was significantly associated with poor overall survival in stage IV melanoma ( = 137; HR 1.810; = 0.006). Furthermore, our data showed that high miR-155-5p expression, which is controlled by DNA methylation at its promoter region (TCGA; Pearson's -0.455; < 0.001), is significantly associated with KPC1 downregulation (JWCI; = 0.028, TCGA; = 0.003). This study revealed novel epigenetic regulation of KPC1 associated with NF-κB pathway activation, promoting metastatic melanoma progression. These findings suggest the potential utility of KPC1 and its epigenetic regulation as theranostic targets. .